U.S. Pat. No. 4,768,347, assigned to the assignee hereof discloses refrigerant recovery system that includes a compressor having an inlet coupled through an evaporator and through a solenoid valve to the refrigeration equipment from which refrigerant is to be withdrawn, and an outlet coupled through a condenser to a refrigerant storage container or tank. The evaporator and condenser are contained within a closed cylindrical canister for heat exchange and oil separation, the canister having an oil drain in the bottom. The refrigerant storage container is carried by a scale having a limit switch coupled to control electronics to prevent or terminate further refrigerant recovery when the container is full. The scale comprises a platform pivotally mounted by a hinge pin to a wheeled cart, which also carries the evaporator/condenser unit, compressor, control electronics, and associated valves and hoses.
U.S. Pat. No. 4,805,416, also assigned to the assignee hereof, discloses systems for recovering, purifying and recharging refrigerant in which, during a purification cycle, refrigerant is circulated from the refrigerant storage container in a closed path through a circulation valve and a filter for removing water and other contaminants, and then returned to the container. U.S. application Ser. No. 263,887, filed Oct. 28, 1988, now U.S. Pat. No. 4,878,356 and also assigned to the assignee hereof, discloses a refrigerant recovery system that includes a refrigerant storage container, refrigeration circuitry for withdrawing refrigerant from equipment under service and feeding such refrigerant to the container for storage, and a scale supporting the container for sensing impending overfill of the container. The scale includes a beam horizontally rigidly cantilevered from a base. A switch is positioned adjacent to the cantilever-remote end of the beam, and is responsive to resilient deflection of the beam to indicate impending overfill of the container, and to prevent or terminate operation of the refrigerant recovery system.
A problem with refrigerant recovery and purification systems disclosed in the noted patents and application lies in use thereof in conjunction with differing types of refrigerants, such as R-12, R-22 and R-502. When it is desired to change refrigerant types in connection with which the system is used, the entire system must be purged to insure that the refrigerants do not become intermixed and contaminated. The recovery compressor can be used to remove essentially all refrigerant from the unit inlet down to the compressor inlet fitting, including the evaporator and the system oil separator. However, to remove refrigerant from the compressor outlet through the compressor oil separator, the condenser and associated output piping requires external input of heat or pumping to clear the system, which cannot be accomplished by the unit it self. For example, the condenser can be externally heated to drive the refrigerant into the storage container, or the container can be cooled to reduce internal pressure and pull refrigerant into the container. As another alternative, an external pump can be employed.
It is a general object of the present to provide a refrigerant handling system and method that include facility for use in connection with multiple differing types of refrigerants without requiring external application of heat or pumping to clear the refrigerant lines. Another and more specific object of the present invention is to provide a refrigerant handling system and method of subject character that facilitate starting of the compressor by equalizing pressure between the compressor inlet and outlet, and/or that include an oil separator at the compressor outlet with facility for returning separated oil to the compressor inlet.